Isoflavone derivatives are believed to possess various physiological and pharmacological activities. For this reason, isoflavone derivatives are used as material for food and pharmaceuticals. As studies uncover the functions of isoflavone derivatives, there have been reports that the estrogen-like activity of isoflavone derivatives is not, as conventionally believed, due to the action of the isoflavone derivatives themselves, but due to the strong estrogen-like activity found throughout the body exhibited by equol, which is absorbed in the intestines after being released from various kinds of intestinal bacteria metabolizing (biosynthesizing) the isoflavone derivatives to produce equol. In humans, not all individuals have the ability to produce equol in the intestines, and such an equol-producing ability varies among different individuals. For example, some individuals may have no equol-producing bacteria in the intestines, while others may have such bacteria, but with only a limited ability to produce equol.
Accordingly, it would be beneficial in countries with aging populations, such as Japan, to make effective use of equol in the body, particularly in consideration of chronic disorders such as osteoporosis affecting the elderly. Given the fact that equol-producing bacteria are not found in all individuals, there is a need to find an equol synthesis material which enables efficient artificial equol production.
Under these circumstances, it is very important, in terms of providing an equol synthesis material, to identify and use enzymes involved in the equol biosynthetic pathway. However, no information is available concerning enzymes producing or catalyzing some of the intermediates involved in the biosynthetic pathway. Accordingly, the identification of enzymes associated with the synthesis of such intermediates is desired.    Patent Document 1: JP-A-2006-296434